Use a -short- custom hash for controlpersist path by default (#20843)

* A method to validate and alter the ssh control path automatically.
* First tries %C to use the shortened hash
* On further failure, it removes section by section from the original path
* Fix hostname
* Implement bcoca's suggested changes
* Remove unused option
* Remove unused class var
* Use to_string to avoid unicode error
* Switch from to_text to to_bytes
* Update the example config for the new controlpath feature

examples/ansible.cfg

@@ -310,16 +310,14 @@
 # control_path_dir = /tmp/.ansible/cp
 #control_path_dir = ~/.ansible/cp
 
-# The path to use for the ControlPath sockets. This defaults to
-# "%(directory)s/ansible-ssh-%%h-%%p-%%r", however on some systems with
-# very long hostnames or very long path names (caused by long user names or
-# deeply nested home directories) this can exceed the character limit on
-# file socket names (108 characters for most platforms). In that case, you
-# may wish to shorten the string below.
+# The path to use for the ControlPath sockets. This defaults to a hashed string of the hostname, 
+# port and username (empty string in the config). The hash mitigates a common problem users 
+# found with long hostames and the conventional %(directory)s/ansible-ssh-%%h-%%p-%%r format. 
+# In those cases, a "too long for Unix domain socket" ssh error would occur.
 #
 # Example:
 # control_path = %(directory)s/%%h-%%r
-#control_path = %(directory)s/ansible-ssh-%%h-%%p-%%r
+#control_path =
 
 # Enabling pipelining reduces the number of SSH operations required to
 # execute a module on the remote server. This can result in a significant